The present invention relates to a spring system for vehicles, especially for motor vehicles, which is arranged between the vehicle wheels and the body, and in which the rear wheel spring system is constructed as active spring system and the vehicle front wheels are constructed as road surface sensors and are operatively connected with the active rear wheel spring system.
Active vehicle spring systems, by means of which the driving safety, on the one hand, and the driving comfort, on the other, are to be increased, are known (DE-OS No. 27 38 455, DE-OS No. 33 08 011. DE-OS No. 34 24 979, DE-OS No. 34 34 757, U.S. Pat. No. 3,124,368; Darenberg, Gall and Acker, "Chancen und Probleme aktiver Kraftfahrzeugfederungen", VDI-Berichte Nr. 515, 1984, Pages 187-194; Fuhrmann, "Aktive Federung fur morgen?", CH-Zeitung Automobil Revue Nr. 46/1983 of Nov. 10, 1983, Page 45). Furthermore, it is known to utilize the deflections, which a vehicle front wheel undergoes as a result of road surface unevennesses and which thus supply information about the road profile, as control magnitudes for the active spring system (EP-OS No. 192 178; Fuhrmann, "Das denkende Fahrwerk", DE-Zeitschrift Mot, Heft 4/1984, Pages 46-48). With the known active vehicle spring systems, an active spring system is always provided both at the vehicle front wheels as also at the vehicle rear wheels. This requires a considerable expenditure.
The present invention is concerned with the task to far-reachingly achieve the advantages, which are connected with an active vehicle spring system, with relatively slight expenditure.
The underlying problems are solved according to the present invention in that that front wheel spring system is constructed as passive spring system while the rear wheel spring system remains constructed as active spring system.
According to the present invention, the sensing signals thus act on an active spring system provided exclusively at the vehicle rear wheels, whereas a passive spring system is provided at the vehicle front wheels.
An optimization is achieved by the present invention which represents a compromise between the conflicting requirements, on the one hand, to keep the expenditure as low as possible and, on the other, to utilize as fully as possible the potential possibilities of an active vehicle spring system.
According to the present invention, a sufficient time interval is available for the activation of the rear wheel spring system. For example, with a wheel base of 2.5 m and a driving velocity of 90 km/h, the spacing with respect to time between the time when the vehicle front wheels drive over a predetermined road location and the vehicle rear wheels pass over the same, amounts to 0.1 s. The available time between the signal detection at the vehicle front wheels and the adjustment of the vehicle rear wheels which takes place after the signal processing, makes it possible to actuate the active spring system with an acceptable power expenditure. Only the usual expenditure for a passive spring system is thereby required for the spring system at the vehicle front wheels.